Altcoin Season Index
By Menno — 13 years in crypto, 3 bear markets survived, zero paid promotions
Last updated: March 2026
The Altcoin Season Index measures what percentage of the top 50 altcoins have outperformed Bitcoin over the past 90 days, with readings above 75 indicating altcoin season.
The Altcoin Season Index, maintained by CoinMarketCap and Blockchaincenter.net, provides a simple quantitative measure of altcoin market performance relative to Bitcoin. The calculation: if 75% or more of the top 50 altcoins outperformed Bitcoin over the last 90 days, the index is in "altcoin season." If 25% or fewer outperformed Bitcoin, it's "Bitcoin season."
This metric captures the rotation that occurs within crypto market cycles. During early and mid bull markets, Bitcoin typically leads. As Bitcoin's gains slow and the cycle matures, capital rotates into Ethereum, then large-cap altcoins, then mid and small caps — each wave amplifying both gains and eventual losses. The full altcoin season rotation (all 50 top altcoins beating Bitcoin) historically occurs in the final 3-6 months before a major cycle top.
Understanding the altcoin season cycle helps with allocation timing. During Bitcoin-dominant phases (index below 25), most altcoins underperform and adding altcoin exposure typically underperforms simply holding more Bitcoin. As the index climbs above 50 and approaches 75, the risk/reward for selective altcoin exposure improves. Once the index exceeds 90, historical data suggests it's often late in the cycle — very high altcoin valuations tend to correct sharply when Bitcoin's momentum fades. The Alpha Factory Altcoin Rules incorporates BTC dominance and relative performance metrics, which directly relate to the altcoin season index.
Frequently Asked Questions
What does an Altcoin Season Index above 75 mean?
An index above 75 means 75%+ of the top 50 altcoins have outperformed Bitcoin in the last 90 days — the textbook definition of altcoin season. This is typically a period of broad altcoin outperformance, high retail interest, and increasing market euphoria. It has historically occurred in the latter stages of bull cycles.
How long does altcoin season typically last?
Based on the 2017 and 2021 cycles, extended altcoin season (index above 75 for multiple weeks) has lasted approximately 3-6 months. However, within that period there are sharp corrections. The 2021 altcoin season from February to May saw many altcoins gain 300-1000%, followed by a 60-90% correction in May-June 2021 before a second wave in October-November.
Related Tools on Alpha Factory
Related Terms
Altcoin Season
Altcoin season (alt season) is a phase in the crypto market cycle when altcoins significantly outperform Bitcoin, often producing 5-50x returns as speculative capital rotates from Bitcoin into smaller coins.
Bitcoin Dominance
Bitcoin dominance is the percentage of the total cryptocurrency market cap held by Bitcoin. When dominance rises, Bitcoin outperforms altcoins. When it falls, altcoins tend to rally (alt season).
Market Cycle
The crypto market cycle is the recurring pattern of accumulation, uptrend, distribution, and downtrend that crypto markets follow — typically tied to Bitcoin's 4-year halving schedule.
Altcoin
An altcoin is any cryptocurrency other than Bitcoin. Altcoins range from large-cap platforms like Ethereum to small-cap speculative tokens, and they typically carry higher risk and higher potential returns than Bitcoin.
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